The present invention relates to an apparatus for reducing the toxic components in the exhaust gas of internal combustion engines by influencing the mass ratio of the fuel-air mixture supplied to the internal combustion engine, effected by varying the keying ratio (duty cycle) of a cyclically actuated electromagnetic valve disposed in the control pressure circuit of an engine fuel supply system. The electromagnetic valve is controlled by a regulating device in response to data from measuring transducers which monitor various operating parameters of the internal combustion engine.
Apparatuses of this type are designed to automatically provide a favorable fuel-air mixture for all operating conditions of the internal combustion engine so as to burn the fuel as completely as possible and thus prevent toxic gases from being produced, or, at least, to considerably reduce the amount of toxic gases while obtaining maximum performance of the internal combustion engine or minimum fuel consumption, as desired. For this purpose, the quantity of fuel must be very accurately metered out in accordance with the requirements of each operating state of the internal combustion engine and the air-fuel ratio must be varied as a function of engine operating parameters such as speed, load, temperature and exhaust gas composition.
In known apparatuses for reducing the toxic components in the exhaust gas of internal combustion engines, an electromagnetic valve, cycled by an electronic regulating device as a function of the operating parameters of the internal combustion engine is disposed in a control pressure circuit for the purpose of varying a control pressure which, in turn, affects the fuel-air ratio. When electronic regulating devices of this type are used in motor vehicles, they are exposed to the effects of temperature and aging which produce undesirable variations in the keying ratio of the electromagnetic valve.